8XC251SA, SB, SP, SQ USER’S MANUAL
3-16
3.4 SPECIAL FUNCTION REGISTERS (SFRS)
The special function registers (SFRs) reside in their associated on-chip peripherals or in the core.
Table 3-5 shows the SFR address space with the SFR mnemonics and reset values. SFR addresses
are preceded by “S:” to differentiate them from addresses in the memory space. Unoccupied lo-
cations in the SFR space (the shaded locations in Table 3-5) are unimplemented, i.e., no register
exists. If an instruction attempts to write to an unimplemented SFR location, the instruction exe-
cutes, but nothing is actually written. If an unimplemented SFR location is read, it returns an un-
specified value.
NOTE
SFRs may be accessed only as bytes; they may not be accessed as words or
dwords.
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